What is the difference between Ni-Cd, Ni-MH, Li-Polymer and Li-ion?

Li-ion (Lithium Ion). This is one of the newest cell types available. It is also the lightest battery type currently available on a commercial basis and can provide more power than other main cell types. There are no known problems of memory effect with this battery type and it is the easiest battery type to care for. The downside of this battery is that it has the highest engineering costs and therefore the price is usually considerably higher than other cell types.

Ni-MH (Nickel Metal Hydride). This cell type is the most common cell type currently available for laptop computers, (although Li-ion is rapidly becoming the most popular) This battery type is relatively cheap to manufacture and therefore tends to be cheaper than Li-ion. This cell type is prone to memory effect so it is important to take good care of your Ni-MH battery to ensure that you obtain the best runtimes.

Ni-Cd (Nickel Cadmium). This is one of the older cell types and is generally only found in older laptops. The main pro for this cell type is its ability to handle higher loads, and therefore is more commonly found in portable power tools or devices that need a lot of power to work efficiently. The main downside of this cell type is that it is notorious for suffering with memory effect so good care must be taken with this battery to ensure most effective use of battery.

Li-Polymer (Lithium Polymer). This type has technologically evolved from lithium-ion batteries. Ultimately, the lithium-salt electrolyte is not held in an organic solvent as in the lithium-ion design, but in a solid polymer composite such as polyethylene oxide or polyacrylonitrile. The battery that is currently available is a hybrid design correctly referred to as a Lithium-Ion polymer battery. The flammable electrolyte is still present but held within the polymer.
The advantages of Li-ion poly over the lithium-ion design include lower cost manufacturing and being more robust to physical damage.

What is the memory effect?

Memory effect, also known as lazy battery effect or battery memory, is an effect usually observed in nickel cadmium rechargeable batteries that causes them to hold less charge. It describes one very specific situation in which certain batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged. The battery appears to "remember" the smaller capacity. The source of the effect are changes of the characteristics of the underused active materials of the cell.
The term is commonly misapplied to almost any case in which a battery appears to hold less charge than was expected. These cases are more likely due to battery age and use, leading to irreversible changes in the cells due to internal short-circuits, loss of electrolyte, or reversal of cells.

Description

High quality OEM Li-Polymer Sony Ericsson battery.

Brand new

Quantity: 1

Sony Ericsson part no: BST-38

Voltage: 3.6V

Capacity: 930 mAh

Note that a new lithium Polymer battery's full performance is only achieved after 2-3 complete charge and discharge cycles.